Since raising $6.5 million in its first major funding round last October, RedPath Integrated Pathology Inc. has doubled its work force and expanded its management team as it prepares to ramp up its sales efforts. The North Side-based biotech company, which provides specialized cancer diagnostic tools for pathologists, oncologists and clinicians, has grown to 22 employees and added three new seasoned executives to help play an integral role in the company’s next stage of development: seeking growth through new partnerships, new clients and greater use of its product by existing clients.